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Category Archives: Physics

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Tyce DeYoung (MSU Department of Physics and Astronomy) colloquium on high-energy astrophysics and exploration of the high-energy universe with the IceCube neutrino detector at the South Pole. Several MSU professors are part of the IceCube collaboration. I predict very exciting developments in neutrino astronomy in the coming decade ;-) The situation is similar to that …

Excerpt from Sidney Coleman’s Erice lectures. The period he describes just predates my entry into physics. This was a great time to be a high-energy theorist, the period of the famous triumph of quantum field theory. And what a triumph it was, in the old sense of the word: a glorious victory parade, full of …

Almost every student who attends a decent high school will be exposed to Special Relativity. Their science/physics teacher may not really understand it very well, may do a terrible job trying to explain it. But the kid will have to read a textbook discussion and (in the internet age) can easily find more with a …

Webpage / Program / Abstracts. My opening remarks: On behalf of Michigan State University it is my pleasure to welcome all of you to this workshop on quantum information science. In the fall of 1983 (my freshman year!) Feynman taught a graduate course at Caltech called Potentialities and Limitations of Computing Machines. Chapter 6 of …

The 36th Annual International Symposium on Lattice Field Theory begins tomorrow, hosted by MSU. My opening remarks are below. No peeking if you are an attendee! LATTICE 2018 Opening Remarks 7/23/2018 Good morning. I’d like to extend my warmest welcome to all of you on behalf of Michigan State University. We are very pleased and …

My office will be recording some of the most interesting of the many talks that happen at MSU. I will post some of my favorites here on the blog. See the MSU Research channel on YouTube for more! Audio for this video isn’t great, but we are making improvements in our process / workflow for capturing these …

The movie “Interstellar” has not only fascinated moviegoers: it also has created a discussion among scientists whether any and all of the science discussed in the movie is accurate. To be sure, this is not the fate that befalls your average Sci-Fi movie where the laws of physics are routinely (and often egregiously) broken over …

Roger Penrose writes in the Guardian, providing a scientifically precise summary of Hawking’s accomplishments as a physicist (worth reading in full at the link). Penrose and Hawking collaborated to produce important singularity theorems in general relativity in the late 1960s. Here is a nice BBC feature: A Brief History of Stephen Hawking. The photo above …

The passing of the great physicist Stephen Hawking today at the age of 76 fills me with sadness for many different reasons. On the one hand, it was inspiring to witness that, seemingly, the power of will and intellect can hold such a serious illness at bay for so long. On the other hand, I …

When I was at Caltech a few weeks ago I had a chance to discuss the recent paper below by Sean Carroll and collaborators. (Authors are at Caltech, Berkeley, and UBC.) Their paper is very clearly written, but probably suitable only for experts who are already familiar with the black hole information paradox. I discussed …

It’s been almost 10 years since I made the post Are you Gork? Over the last decade, both scientists and non-scientists have become more confident that we will someday create: A. AGI (= sentient AI, named “Gork” :-) See Rise of the Machines: Survey of AI Researchers. B. Quantum Computers. See Quantum Computing at a Tipping …

I received an email from a physicist colleague suggesting that we might be near a “tipping point” in quantum computation. I’ve sort of followed quantum computation and quantum information as an outsider for about 20 years now, but haven’t been paying close attention recently because it seems that practical general purpose quantum computers are still …

Today I came across a recent interview with Ed Witten in Quanta Magazine. The article has some nice photos like the one above. I was struck by the following quote from Witten (“It from Qubit!”): When I was a beginning grad student, they had a series of lectures by faculty members to the new students about …

Science reports on MSU’s Facility for Rare Isotope Beams, which will probe the properties of nuclear matter. Science: Last month, astronomers wowed the world when they announced that they had seen two neutron stars merge, apparently creating heavy elements such as gold and platinum and spewing them into space. Nuclear physicists here at Michigan State …

This is video of an excellent talk on the human connectome by neuroscientist Bobby Kasthuri of Argonne National Lab and the University of Chicago. (You can see me sitting on the floor in the corner :-) The story below is for entertainment purposes only. No triggering of biologists is intended. The Physicist and the Neuroscientist: A …

In this public lecture Weinberg explains the problems with the two predominant interpretations of quantum mechanics, which he refers to as Instrumentalist (e.g., Copenhagen) and Realist (e.g., Many Worlds). The term “interpretation” may be misleading because what is ultimately at stake is the nature of physical reality. Both interpretations have serious problems, but the problem …

This is the best technical summary of the Los Alamos component of the Manhattan Project that I know of. It includes, for example, detail about the hydrodynamical issues that had to be overcome for successful implosion. That work drew heavily on von Neumann’s expertise in shock waves, explosives, numerical solution of hydrodynamic partial differential equations, …

In the natural world, cooperation is everywhere. You can see it among people, of course, but not everybody cooperates all the time. Some people, as I’m sure you’ve heard or experienced, don’t really care for cooperation. Indeed, if cooperation were something that everybody does all the time, we wouldn’t even talk about it: we’d take …

I have not, until recently, invested significant time in trying to understand climate modeling. These notes are primarily for my own use, however I welcome comments from readers who have studied this issue in more depth. I take a dim view of people who express strong opinions about complex phenomena without having understood the underlying …

How Alexander Sachs, acting on behalf of Szilard and Einstein, narrowly convinced FDR to initiate the atomic bomb project. History sometimes hangs on a fragile thread: had the project been delayed a year, atomic weapons might not have been used in WWII. Had the project completed a year earlier, the bombs might have been used …

Pitts is one of the least studied geniuses of the early information age. See also Wikipedia, Nautil.us. Cabinet Magazine: There are no biographies of Walter Pitts, and any honest discussion of him resists conventional biography. Pitts was among the original participants in the mid-century cybernetics conferences, though he began his association with that group of …

I love Joe Rogan — he has an open, inquisitive mind and is a sharp observer of life and human society. See, for example, this interview with Dan Bilzerian about special forces, professional poker, sex, drugs, heart attacks, life, happiness, hedonic treadmill, social media, girls, fame, prostitution, money, steroids, stem cell therapy, and plenty more. …

This was on the new books table at our local bookstore. I had almost forgotten about doing an interview and corresponding with the author some time ago. See also here and here. The book is a well-written overview of some of the more theoretical aspects of inflationary cosmology, the big bang, the multiverse, etc. It also …

I think I’ve made this Google drive folder publicly readable. It contains slides for many talks I’ve given over the years, going back almost to 2000 or so. Topics include black hole information, monsters in curved space, entanglement entropy, dark energy, insider’s guide to startups, the financial crisis of 2008, foundations of quantum mechanics, and …

Oppenheimer on Bohr (1964 UCLA) I came across this 1964 UCLA talk by Oppenheimer, on his hero Niels Bohr. Oppenheimer: Mathematics is “an immense enlargement of language, an ability to talk about things which in words would be simply inaccessible.” I find it strange that psychometricians usually define “verbal ability” over a vocabulary set that …

Are quanta particles or waves? The title of this post is an age-old question isn’t it? Particle or wave? Wave or particle? Many have rightly argued that the so-called “wave-particle duality” is at the very heart of quantum weirdness, and hence, of all of quantum mechanics. Einstein said it. Bohr said it. Feynman said it. …

My kids have been reading lots of books over the break, including an adventure series that involves time travel. Knowing vaguely that dad is a theoretical physicist, they asked me how time travel works. 1. Can one change history by influencing past events? OR 2. Is there only one timeline that cannot be altered, even …

Over the holiday I started digging through my mom’s old albums and boxes of photos. I found some pictures I didn’t know existed! Richard Feynman and the 19 year old me at my Caltech graduation: With my mom that morning — hung-over, but very happy! I think those are some crazy old school Ray Bans …

Arrival is based on a short story by Ted Chiang: Story of Your Life. Despite what some have said, the main plot idea (as I remember from the story; I have yet to see the film) goes well beyond the Sapir-Whorf hypothesis — it also requires that human consciousness (potentially) extend beyond the confines of the usual time …

The scale of … triumph cannot be exaggerated. He … had brought about a complete transformation of the European international order. He had told those who would listen what he intended to do, how he intended to do it, and he did it. He achieved this incredible feat without commanding an army, and without the …

After 25+ years in theoretical physics research, the pattern has become familiar to me. Talented postdoc has difficulty finding a permanent position (professorship), and ends up leaving the field for finance or Silicon Valley. The final phase of the physics career entails study of entirely new subjects, such as finance theory or machine learning, and developing …

Google knows enough about me that my YouTube feed now routinely suggests content of real interest. A creepy but positive development ;-) Today YouTube suggested this video of Murray Gell-Mann talking about Everett, decoherence, and quantum mechanics. I had seen this video on another web site years ago and blogged about it (post reproduced below), …

George Dyson is Freeman’s son. I believe this talk was given at SciFoo or Foo Camp. More Ulam (neither he nor von Neumann were really logicians, at least not primarily). Wikipedia on Monte Carlo Methods. I first learned these in Caltech’s Physics 129: Mathematical Methods, which used the textbook by Mathews and Walker. This book was …

My old friend Mark Alford (WUSTL) was on campus last week for the inaugural meeting of the FRIB-TA (Facility for Rare Ion Beams Theory Alliance). Over beers he told me he had come up with a pedagogical way to explain Bell’s inequality in a single picture. Here it is. Ghostly action at a distance: a …

So this is the final installment of the “On quantum measurement” series. You may have arrived here by reading all previous parts in one sitting (I’ve heard of such feats in the comments). This is the apotheosis: what all these posts have been gearing up to. If, for some reason that only the Internets know, …

By now you’ve probably heard that Moore’s Law is really dead. So dead that the semiconductor industry roadmap for keeping it on track has more or less been abandoned: see, e.g., here, here or here. (Reported on this blog 2 years ago!) What I have not yet seen discussed is how a significantly reduced rate …

Live-blogging the LIGO announcement of detection of gravity waves. Detection of an event in 2015 (initial science run of advanced LIGO) is good news for the future use of gravity waves as an astrophysical probe — it suggests a fairly high density of NS-NS, NS-BH, and BH-BH binaries in the universe. Each time astronomers have …

A recent paper by Hawking, Perry, and Strominger (Soft Hair on Black Holes) proposes a new kind of soft hair (i.e., soft gravitons or photons) on the black hole horizon. This hair is related to recent results on BMS symmetries and soft (zero) modes by Strominger and collaborators. The existence of an infinite number of …

I am a Quantum Engineer, but on Sundays I have principles. — J.S. Bell My own conclusion … there is no interpretation of quantum mechanics that does not have serious flaws. — Steve Weinberg I wrote this paper mainly for non-specialists: any theorist should be able to read and understand it. However, I feel the …

Radar and nuclear weapons could not have been developed without the big brains. Feynman’s War: Modelling Weapons, Modelling Nature Peter Galison* What do I mean by understanding? Nothing deep or accurate—just to be able to see some of the qualitative consequences of the equations by some method other than solving them in detail. — Feynman …

In this earlier post I advocated for cognitive filtering via study of hard subjects Thought experiment for physicists: imagine a professor throwing copies of Jackson’s Classical Electrodynamics at a group of students with the order, “Work out the last problem in each chapter and hand in your solutions to me on Monday!” I suspect that …

The visit of SOAR was not on our original itinerary, but I asked to visit and my wish was granted (thanks Tim Spuck!). SOAR is just a jaunt down the road from Gemini on the same peak of Cerro Pachon. The reason I wanted to go was because my employer, the Physics-Astronomy department at MSU is one …

Editorial in the Lancet, reflecting on the Symposium on the Reproducibility and Reliability of Biomedical Research held April 2015 by the Wellcome Trust. Offline: What is medicine’s 5 sigma? … much of the [BIOMEDICAL] scientific literature, perhaps half, may simply be untrue. Afflicted by studies with small sample sizes, tiny effects, invalid exploratory analyses, and …

Regular readers will know that I’ve been interested in the so-called Teller-Ulam mechanism used in thermonuclear bombs. Recently I read Kenneth Ford‘s memoir Building the H Bomb: A Personal History. Ford was a student of John Wheeler, who brought him to Los Alamos to work on the H-bomb project. This led me to look again …

Here’s to you, quantum measurement afficionado, who has found their way to the sixth installment, breathless (I hope), to learn of the fate of the famous cat, eponymous with one of the great ones of quantum mechanics. Does she live or die? Can she be both dead and alive? What did this kitten ever do …

This is v2 of a draft we posted earlier in the year. The new version has much more detail on whether rotation curve measurements of an isolated dwarf galaxy might be able to constrain the local dark energy density. As we state in the paper (c is the local dark energy density): In Table V, …

Theoretical physicist John Hopfield, inventor of the Hopfield neural network, on the differences between physics and biology. Hopfield migrated into biology after making important contributions in condensed matter theory. At Caltech, Hopfield co-taught a famous course with Carver Mead and Richard Feynman on the physics of computation. Two cultures? Experiences at the physics-biology interface (Phys. …

New paper! We hypothesize that rapid growth of entanglement entropy between modes in the central region and other scattering degrees of freedom is responsible for fast thermalization in heavy ion collisions. Entanglement and Fast Quantum Thermalization in Heavy Ion Collisions (arXiv:1506.03696) Chiu Man Ho, Stephen D. H. Hsu Let A be subsystem of a larger …